Nanomechanics of Nanocomposites
Catherine Brinson (Northwestern University)
Prager Medal Symposium in honor of George Weng: Micromechanics, Composites and Multifunctional Materials
Mon 4:20 - 5:40
MacMillan 117
Nanostructured polymers offer advances in structural and functional materials from lightweight materials for aerospace to drug delivery devices to solar and battery applications. However, the deliberate construction of nanostructured polymers and predicting their ultimate properties remains a black art. This talk will present a number of different approaches to design nanostructured polymers and discuss the influence of structure and components on their properties. One issue of paramount importance is the concept of interface and interphase – a nanoscale structure implies that all polymer chains are within 10s to 100s of nanometers from an interface. While the local dynamics of thin polymer films have been studied in detail in the past two decades, development of an understanding of local mechanical properties has been hindered by complex in situ geometries and by the proximity of stiff substrates in simple thin film model systems: mechanical measurements are confounded by interaction with the substrate, convoluting polymer and substrate properties. Several new approaches are presented to determine local, nanometer scale properties of soft materials, specifically applied to polymers. Nanoindentation and AFM experiments coupled with numerical simulations applied to thin polymer films reveal separately the effects of substrate and interphase near attractive and non-attractive interfaces. Results demonstrate that both surfaces significantly affect the mechanical properties of the polymer up to hundreds of nanometers from the interface. Data also sheds light on the roles of confinement and chemistry on mechanical properties. Our results open the doors to new fundamental understanding of interfacial and small-scale behavior in polymers and other soft materials as well as application advances in nanocomposites, microelectronics and biopolymers.